This article requires a subscription to view the full text. If you have a subscription you may use the login form below to view the article. Access to this article can also be purchased.

Significance

The molecular basis of the mysterious ability of the clinically approved bioresorbable vascular scaffold to maintain radial strength after 9 mo of hydrolysis—despite a ∼40% reduction in the poly l-lactide molecular weight Mn—is an unexpected gradient in degradation revealed by X-ray microdiffraction. Hydrolysis is slowest in the 100- × 30-µm region where stress is concentrated during arterial contractions. This favorable gradient in hydrolysis arises from gradients in morphology created during crimping onto the angioplasty balloon: Small regions that undergo elongational deformation (<3% of scaffold) resist hydrolysis after deployment. This remarkably small amount of material (too low to detect in Mn measurements) has a disproportionate impact on strength because it forms precisely where the scaffold is most vulnerable to failure.

Abstract

Biodegradable polymers open the way to treatment of heart disease using transient implants (bioresorbable vascular scaffolds, BVSs) that overcome the most serious complication associated with permanent metal stents—late stent thrombosis. Here, we address the long-standing paradox that the clinically approved BVS maintains its radial strength even after 9 mo of hydrolysis, which induces a ∼40% decrease in the poly l-lactide molecular weight (Mn). X-ray microdiffraction evidence of nonuniform hydrolysis in the scaffold reveals that regions subjected to tensile stress during crimping develop a microstructure that provides strength and resists hydrolysis. These beneficial morphological changes occur where they are needed most—where stress is localized when a radial load is placed on the scaffold. We hypothesize that the observed decrease in Mn reflects the majority of the material, which is undeformed during crimping. Thus, the global measures of degradation may be decoupled from the localized, degradation-resistant regions that confer the ability to support the artery for the first several months after implantation.

Footnotes

Author contributions: K.R. and J.A.K. designed research; K.R. and T.D.L. performed research; A.A., M.B.K., and J.P.O. contributed new reagents/analytic tools; K.R. and J.A.K. analyzed data; and K.R. and J.A.K. wrote the paper.

Conflict of interest statement: M.B.K. and J.P.O. are employees of Abbott Vascular. Funding for this research was provided by Abbott Vascular.

Researchers report biparental inheritance of mitochondrial DNA in 17 members of three unrelated multigeneration families, paving the way for insights into alternative mechanisms for the treatment of inherited mitochondrial diseases.

Researchers report a machine-learning approach to identify land plants at risk of extinction, suggesting that the approach can be used to guide policies aimed at allocating resources for biodiversity conservation.

A study explores how cats groom fur using fine structures called papillae on the surface of the tongue and presents a biologically inspired hairbrush to remove allergens from cat fur and apply medications on cat skin.